/*
 * Copyright (c) 2005, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package com.sun.imageio.plugins.common;

import java.io.IOException;
import java.io.PrintStream;
import javax.imageio.stream.ImageOutputStream;

/*
 * Modified from original LZWCompressor to change interface to passing a
 * buffer of data to be compressed.
 */
public class LZWCompressor {

  /**
   * base underlying code size of data being compressed 8 for TIFF, 1 to 8 for GIF
   **/
  int codeSize;

  /**
   * reserved clear code based on code size
   **/
  int clearCode;

  /**
   * reserved end of data code based on code size
   **/
  int endOfInfo;

  /**
   * current number bits output for each code
   **/
  int numBits;

  /**
   * limit at which current number of bits code size has to be increased
   **/
  int limit;

  /**
   * the prefix code which represents the predecessor string to current input point
   **/
  short prefix;

  /**
   * output destination for bit codes
   **/
  BitFile bf;

  /**
   * general purpose LZW string table
   **/
  LZWStringTable lzss;

  /**
   * modify the limits of the code values in LZW encoding due to TIFF bug / feature
   **/
  boolean tiffFudge;

  /**
   * @param out destination for compressed data
   * @param codeSize the initial code size for the LZW compressor
   * @param TIFF flag indicating that TIFF lzw fudge needs to be applied
   * @throws IOException if underlying output stream error
   **/
  public LZWCompressor(ImageOutputStream out, int codeSize, boolean TIFF)
      throws IOException {
    bf = new BitFile(out, !TIFF); // set flag for GIF as NOT tiff
    this.codeSize = codeSize;
    tiffFudge = TIFF;
    clearCode = 1 << codeSize;
    endOfInfo = clearCode + 1;
    numBits = codeSize + 1;

    limit = (1 << numBits) - 1;
    if (tiffFudge) {
      --limit;
    }

    prefix = (short) 0xFFFF;
    lzss = new LZWStringTable();
    lzss.clearTable(codeSize);
    bf.writeBits(clearCode, numBits);
  }

  /**
   * @param buf data to be compressed to output stream
   * @throws IOException if underlying output stream error
   **/
  public void compress(byte[] buf, int offset, int length)
      throws IOException {
    int idx;
    byte c;
    short index;

    int maxOffset = offset + length;
    for (idx = offset; idx < maxOffset; ++idx) {
      c = buf[idx];
      if ((index = lzss.findCharString(prefix, c)) != -1) {
        prefix = index;
      } else {
        bf.writeBits(prefix, numBits);
        if (lzss.addCharString(prefix, c) > limit) {
          if (numBits == 12) {
            bf.writeBits(clearCode, numBits);
            lzss.clearTable(codeSize);
            numBits = codeSize + 1;
          } else {
            ++numBits;
          }

          limit = (1 << numBits) - 1;
          if (tiffFudge) {
            --limit;
          }
        }
        prefix = (short) ((short) c & 0xFF);
      }
    }
  }

  /*
   * Indicate to compressor that no more data to go so write out
   * any remaining buffered data.
   *
   * @exception IOException if underlying output stream error
   */
  public void flush() throws IOException {
    if (prefix != -1) {
      bf.writeBits(prefix, numBits);
    }

    bf.writeBits(endOfInfo, numBits);
    bf.flush();
  }

  public void dump(PrintStream out) {
    lzss.dump(out);
  }
}
